org.dspace.importer.external.service.components

Class AbstractRemoteMetadataSource

java.lang.Object

org.dspace.importer.external.service.components.AbstractRemoteMetadataSource

Direct Known Subclasses:

AbstractImportMetadataSourceService

public abstract class AbstractRemoteMetadataSource
extends Object

This class contains primitives to handle request timeouts and to retry requests. This is achieved by classifying exceptions as fatal or as non fatal/retryable. Evidently only subclasses can make the proper determination of what is retryable and what isn't. This is useful in case the service employs throttling and to deal with general network issues.

Author:

Roeland Dillen (roeland at atmire dot com), Antoine Snyers (antoine at atmire dot com)

Field Summary

Fields

Modifier and Type	Field and Description
protected Exception	error
protected Map<Class,List<SourceExceptionHandler>>	exceptionHandlersMap
protected long	interRequestTime
protected long	lastRequest
protected ReentrantLock	lock
protected int	maxRetry
protected String	operationId
protected int	retry
protected String	warning

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractRemoteMetadataSource() Constructs an empty MetadataSource class object and initializes the Exceptionhandlers

Method Summary

Modifier and Type	Method and Description
Exception	getError() Retrieve the last encountered exception
protected List<SourceExceptionHandler>	getExceptionHandler(Exception exception) Retrieve a list of SourceExceptionHandler objects that have an instanceof the exception configured to them.
int	getMaxRetry() Return the number of max retries that can be undertaken before separate functionality kicks in
String	getOperationId() Retrieve the operationId
int	getRetry() Return the number of retries that have currently been undertaken
String	getWarning() Return the warning message used for logging during exception catching
protected void	handleException(int retry, Exception exception, String operationId) Handles a given exception or throws on a MetadataSourceException if no ExceptionHandler is set
abstract void	init() Attempts to init a session
protected void	initExceptionHandlers() initialize the exceptionHandlersMap with an empty LinkedHashMap
protected <T> T	retry(Callable<T> callable) Command pattern implementation.
void	setError(Exception error) Set the last encountered error
void	setMaxRetry(int maxRetry) Set the number of maximum retries before throwing on the exception
void	setWarning(String warning) Set the warning message used for logging
protected void	throwSourceException(int retry, Exception exception, String operationId) Throw a MetadataSourceException
protected void	throwSourceExceptionHook() A specified point where methods can be specified or callbacks can be executed

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

lastRequest

protected long lastRequest

interRequestTime

protected long interRequestTime

lock

protected ReentrantLock lock

maxRetry

protected int maxRetry

retry

protected int retry

operationId

protected String operationId

warning

protected String warning

exceptionHandlersMap

protected Map<Class,List<SourceExceptionHandler>> exceptionHandlersMap

error

protected Exception error

Constructor Detail

AbstractRemoteMetadataSource

protected AbstractRemoteMetadataSource()

Constructs an empty MetadataSource class object and initializes the Exceptionhandlers

Method Detail

initExceptionHandlers

protected void initExceptionHandlers()

initialize the exceptionHandlersMap with an empty LinkedHashMap

getWarning

public String getWarning()

Return the warning message used for logging during exception catching

Returns:

a "warning" String

setWarning

public void setWarning(String warning)

Set the warning message used for logging

Parameters:

warning -

getRetry

public int getRetry()

Return the number of retries that have currently been undertaken

Returns:

the number of retries

getMaxRetry

public int getMaxRetry()

Return the number of max retries that can be undertaken before separate functionality kicks in

Returns:

the number of maximum retries

setMaxRetry

public void setMaxRetry(int maxRetry)

Set the number of maximum retries before throwing on the exception

Parameters:

maxRetry -

getOperationId

public String getOperationId()

Retrieve the operationId

Returns:

A randomly generated UUID. generated during the retry method

getError

public Exception getError()

Retrieve the last encountered exception

Returns:

An Exception object, the last one encountered in the retry method

setError

public void setError(Exception error)

Set the last encountered error

Parameters:

error -

retry

protected <T> T retry(Callable<T> callable)
               throws MetadataSourceException

Command pattern implementation. the callable.call method will be retried until it either succeeds or reaches the try limit. Maybe this should have a backoff algorithm instead of waiting a fixed time.

Type Parameters:

T - return type. Generics for type safety.

Parameters:

callable - the callable to call. See the classes with the same name as the public methods of this class.

Returns:

The result of the call

Throws:

MetadataSourceException - if something unrecoverable happens (e.g. network failures)

handleException

protected void handleException(int retry,
                               Exception exception,
                               String operationId)
                        throws MetadataSourceException

Handles a given exception or throws on a MetadataSourceException if no ExceptionHandler is set

Parameters:

retry - The number of retries before the exception was thrown on

exception - The exception to handle

operationId - The id of the operation that threw the exception

Throws:

MetadataSourceException - if no ExceptionHandler is configured for the given exception

getExceptionHandler

protected List<SourceExceptionHandler> getExceptionHandler(Exception exception)

Retrieve a list of SourceExceptionHandler objects that have an instanceof the exception configured to them.

Parameters:

exception - The exception to base the retrieval of SourceExceptionHandler on

Returns:

a list of SourceExceptionHandler objects

throwSourceException

protected void throwSourceException(int retry,
                                    Exception exception,
                                    String operationId)
                             throws MetadataSourceException

Throw a MetadataSourceException

Parameters:

retry - The number of retries before the exception was thrown on

exception - The exception to throw

operationId - The id of the operation that threw the exception

Throws:

MetadataSourceException

throwSourceExceptionHook

protected void throwSourceExceptionHook()

A specified point where methods can be specified or callbacks can be executed

init

public abstract void init()
                   throws Exception

Attempts to init a session

Throws:

Exception